1. Field of the Invention
The present invention relates to a rotary feeder, especially it is concerned with a sealed rotary feeder which can withstand a large pressure drop between its upstream and its downstream end.
2. Description of the Prior Art
Recently it has become necessary to reuse waste parts made of synthetic resin, for environmental reasons, and it is general practice to separate waste parts and reuse them as material for new products. It is, furthermore, general practice to coat products with a thermosetting coating to add to the beauty of the products.
In the case of liquefying waste parts with a coating, the thermosetting coating is not decomposed. Therefore, the strength of the material is degraded when synthetic resins containing un-decomposed coatings are reused.
For instance, in cold districts, the strength of bumpers made of synthetic resins containing un-decomposed coatings is lower than that of bumpers made of synthetic resin without the coatings included.
The degradation of material strength can be avoided if the coating is removed, but perfect removal of coating is too difficult. Although coating can be mechanically removed by shotblasting etc., it not only takes a long time but is impossible to perfectly remove the coating when parts have complicated shapes. Mechanical removal, therefore, is unsuitable for mass recycling.
Although removal of the coating with organic acid has been proposed, it causes environmental pollution.
To solve the above-mentioned problem, the present applicant has already proposed a method for recycling synthetic resin parts, that is, the coating thereof is hydrolyzed and kneaded into synthetic resin chips (See Japanese Patent Application No. 3-192431).
The above-mentioned method is a so-called batch process, and is not suitable for continuous recycle.
To hydrolyze synthetic resin chips, it is necessary to continuously supply chips to a hydrolyzing vessel, in which the temperature and pressure thereof are maintained at suitable levels.
Prior art of an apparatus enabling a continuous supply of chips under pressure is disclosed in Japanese Unexamined Utility Model Application (Kokai) 55-117438. In this Prior Art, sealing blades of a rotary feeder are pressed against an inner wall of its casing by springs.
It is necessary, therefore, that the more the pressure difference between the inlet and the outlet of the rotary feeder is increased, the more the spring force to press the sealing blades against the inner wall is increased. This causes damage to the sealing blades. Then the life of the blades may be reduced and frequent maintenance and inspection may be required.
The sealing blades in the Prior Art, furthermore, are only inserted into a channel arranged on a rotor. Then when the supplied chips go into the clearance between the sealing blades and the channel, the sealing effect may be lost.